Acetic acid is a widely used chemical. Acetic acid has the chemical formula CH3CO2H and is sometimes also known as ethanoic acid or methanecarboxylic acid. It is commonly abbreviated as MeCO2H, MeCOOH, AcOH, and AA. Acetic acid is a major feedstock in the chemical and polymer industries. As the key component of vinegar, acetic acid also has many applications in food.
Acetic acid can contain various impurities, which can include aldehydes (e.g., acetaldehyde and formaldehyde), formic acid, acrylic acid, water, inorganic and organic salts, and various other compounds. The levels of impurities can depend on the method of production of acetic acid. One commonly used test of the purity of acetic acid is the permanganate test. The permanganate test measures oxidizable impurities present in acetic acid. A quantity of permanganate, e.g., a standardized solution, can be added to a concentrated sample of acetic acid, creating a colored solution. Fading of the characteristic pink color of permanganate indicates consumption of permanganate through reaction with oxidizable impurities. The time over which the pink color of permanganate survives can be described as the “permanganate time,” and samples of acetic acid with long permanganate time can be inferred to contain low levels of oxidizable impurities. Acetic acid that passes the permanganate test (i.e., acetic acid with low levels of oxidizable impurities) can be particularly valuable in applications that demand high purity acetic acid.
Industrially produced acetic acid often contains oxidizable impurities and fails the permanganate test. Various processes and systems for purifying acetic acid are described in the literature. However, there remains a need in the art for improved processes and systems for purification of acetic acid, including processes and systems capable of removing oxidizable impurities from acetic acid.